Tool driving means and control therefor



May 27, 1952 o. w. GREENBERG TOOL DRIVING MEANS AND CONTROL THEREFOR Filed April 19, 1947 2 SHEETS-SHEET l lllllllll ll ll ll lllllllllll I INVENTOR. Mix/fi May 27, 1952 o. w. GREENBERG TOOL DRIVING MEANS AND CONTROL THEREFOR Fil'd April 19, 1947 2 SHEETS-SHEET 2 INVENTUR- Patented May 27 1952 OFFICE TOOL DRIVING MEANS AND CONTROL THEREFOR Otto W. Greenberg, Ocean City, N. J. Application April 19, 1947, Serial No. 742,670

3 Claims.

This invention relates to the method and apparatus for the photo-electric production of halftone cuts employed for printing and has particular reference to the tool mechanism for forming depressions in the surface of a printing plate, to the plates and characteristics of the plates employed in connection with the methods of this invention and to the means for enlarging and reducing the reproductions.

The object of the invention is to obtain less critical or more positive reactions to the signals from the copy than has hitherto been obtained in machines of this class, at the same time to .provide a simple, practical method for obtaining satisfactory printing plates from copies defective in tone values and to provide plates applicable for use in connection with the method employed in this invention. In general, this invention is an improvement over that shown and described in my Patent No. 2,086,798 of July 13, 1937.

The present invention may be carried out by means differing from those disclosed herewith without departingfrom the spirit of the invention. Therefore, the disclosures herewith are to be understood as illustrative rather than in a limited sense. a

Fig. 1 is an assembly elevation of the machine, partly diagrammatic.

Fig. 2 is an end view of Fig. 1.

Fig. 3 is a section on line 33 of Fig. 1.

Fig. 4 is a plan, largely diagrammatic, showing a means that may be employed to reciprocate and to feed the plate in relation to a tool.

Fig. 5 is an enlarged end view of the tool mechanism.

Figs. 6, '7 and 8 are side views of Fig. 5 showing various phases in the operation of the tool and associated parts.

Fig. 9 is an enlarged horizontal section in line with the stem of the tool.

Fig. 10 is a front view of a modified form of spring associated with the tool.

Fig. 11 illustrates an enlarged portion of a porous plate modified for use in my machine,

ward. A second and similar upright rectangular frame I!) is adapted to slide forward and backward in a plane parallel to the first frame 9 in like dovetailed grooves l I and If.

A copy carriage I3 for the copy l4, secured in any suitable manner, is mounted to slide up and down between tracks formed in thesides of the upright rectangular frame 9. A similar carriage 15 for the printing plate I6, secured in any suitable manner, is similarly mounted to slide up and down on the other rectangular frame It].

Reciprocating motion, forward and backward is imparted to the rectangular frame I0 and. with it the plate carriage and plate [6 by a threaded shaft l1 operatively connected to a reversing motor It, by means of a nut 19 on a bracket 20 extending from the rectangular frame it). Feeding motion is imparted to the plate carriage l5 and, with it, to the printing plate l6 by a threaded spindle 2| journaled above and below in the rectangular frame l0 and threaded in the plate carriage. A ratchet 22 at the lower end of the spindle provides means for revolving the spindle step by step, as will be more fully described hereafter.

Motion of the copy carriage l3, corresponding to the plate carriage I5, is obtained by means of a single bar pantograph 23. A sleeve 24, axially adjustable along the length of the bar 23, is mounted on the lower end of a standard 25 by means of a universal joint 26. The standard 25 is adjustably held in a slot 27 in the frame and secured by a bolt 28 at such point along the slot as will give the required reduction or enlargement. One end of the bar 23 is connected by a universal joint to a bracket 29 hinged, as here shown at 36, along the lower edge of the plate carriage i5 and is connected at the other end by a universal joint to a similar bracket 3! along the lower edge of the copy carriage l3 at 32. The brackets 29 and 3! widen out at their attachments to their respective carriages so that they will more readily transfer motion not only up and down, but sidewise as well. They may, in fact, be hinged to the sides of the carriages.

As shown in broken lines in Fig. 1, the brackets compensate for the apparent shortening of the pantograph bar as it sweeps into angular positions vertically or horizontally. It does this in a way mechanically more practical than in devices hitherto employed to this end wherein the pantograph bar is designed to telescope or wherein axially extensive devices are provided at the connecting ends of the bar. The brackets permit greater angular sweeps of the pantograph tion 36, engages adjustable sleeves 31 on the rod 33 at the end of each stroke. When the switch 35, establishes a connection betweenzthe binding" posts 38, and 39, the wiring to the reversing: motor I8, is so connected that the electriccircuit established causes the motor to revolve in one direction, and when binding posts';38.and .40. are;

connected, it revolves in the opposite direction.

When the switch 36 establishes a momentary connection between the binding posts 38 and M asiit sweepsfrom one "side to the othen'the wiring toiasolenoid 42 is such that it is momentarily energized by a current and actuates the pawl 22 to feed the plate carriage l5.- A spring fixed to an extension of the solenoid armature withdraws the armature from the solenoid.

The scanning elements which are associated withthe copy I4 to be reproduced are shown diagrammatically" and include a light source 68 optical system and photo-electric cell 6|. The output of thephoto-electric cell is shown connectedto' the input of an aperiodic amplifier 62 whose output in turn is connected to the electromagnetic control mechanism for thetool.

A'non -magnetic metallic lever 43 is employed to' reciprocate the tool mechanism to and from thesnrfaceof'the printing plate 16. It is fulcrumed' atits'lower end on a'stud 44 projecting fromastandardfi and recipro'cated by an eccentricpin46 revolving in a slot formed in the body oflthe' lever 43. The eccentric pin 46 is carried onthe end of the'shaft 4! geared to the motor lB'b'yLtW'o'sets of bevels 48 and, shown in Fig. 2'.

The poles Ell-of an electro-magnet are fixed to each side of the upper end of the non-magnetic lever43 and reciprocate with it. To avoid reciprocation of the entire electro-magnet, core andcoil included, I have devised a novel construction. For clarity'of description, the core may be said to have been cutoff from the poles, inan arc with the fulcrum 44' of the lever 43 ascenter and then fixed in a position such that substantial continuity of magnetic flux will be maintained betweenthe .core and poles, though the latter are reciprocated. The-core and coil of the electro-magnet Stare shown fi'xedto. the upper end of the standard but separated therefrom-by a non-magnetic disk 51 to avoid stray magnetic flux.

An armature53, bridging the poles, is attached to a non-magnetic stem-54, thefree end of which carries a tapered indenting'tool 55 and:a spring 56, hereinafter again referredto'; The stem 54 preferably square: in: cross section, has free axial play in bearings 51 embedded between .the'poles, Fig. 9. When the electro-magnet'is energized, the armature is held against the poles by the magnetic attraction, which together. with the tool and spring 56, reciprocateswith the poles.

The point of the tool ispositioned in close enough relation to the surface of the printing plate 16 to enable it to penetratethe surface a maximum depth on each forward stroke, provided the driving force, derived from the motor I8 is not discontinued by release of the armature from the poles.

The reaction to the work of compression increases, of course, from zero to maximum from the instant the point of the tool makes contact with the plate until maximum depth is attained. When the tool reaches a depth such that the reactionovercomes thewmagneticholdl on the armature, the arm'ature is released and.- the compression ceases for that'throw of the tool. The strength of the current flowing through the electro-magnet at any given time is a function of thelight reflectedirom the unit area of the copy picked up by the photo-electric cell and determines at what depth of compression the armature releases, which in turn determines the area of. thea-dotithatnwill appear white in the print.

However, due to the inertia of the armature and tool" elements, the point of the tool will penetrate the surface of the-"plate to a certain depth independently of that due to the current inzthe electro-magnet. Thus, the depths obtained:.are

not truly a functiontofthe strength of current:v

I overcome thisdefect' in reproduction by ad? justin'g the spring: 56 to lead therpoint. of the,

tool in contacting: the plate, an amount: such" that when compressed; it: will :react against the tool and the force ofinertiabehindit:

Furthermore, at low. current": strengths, justabove zero, the hold on the;armature istoo:critical to produce proportionally 'minutei depths: of

depression. I overcomethissdefect' in satisfactory reproduction by adding tension tothe spring; 55 to provide greaterxresistance. toizthez toohso that the current strength inthe electro-magnetcan be increased to asatisia'ctoryaminhnumi The spring '58 also serves-to withdrawthepcint of' the toolaway r from the plateiquicklyt at the instant of armaturerelease: Another functionrcfthe spring fifi; is toiprotecttheupointofithe tool and prevent its scratching the surface of the plate when inserting or removing the: platefrom its carriage;

The spring 56 is shownv in; the form of: a. coil except in Figs. 9and il0;where asbladmspring is shown formed into an oval-like; shape. This spring or resilient element may take, anyone of many shapes and forms-Jandibezmountedin a variety of ways withoutdepartmg-fromi' the spirit of the invention. Toprevent it pressing too heavily againstflnished; or'indentedareasof the plate, the spring'is' designed: to contact the surfaces not yet: indented; This is illustrated in Figs. 9 and 10, where abossiiiisshownformed on the blade spring just below the'tool opening, the advancing direction of the toolin relation to-plate travel as indicated bytthe arrows.

Referringto Figs: 6, 7 and 8, a. succession .of phases in the reciprocation of thelever and the tool mechanismisillustrated; InsFig; 6, theforward throw is nearly completed. The-tool spring isshown compressed with the tool penetrating the plate. In the next: phase; Fig. 7, the throwfo-rward is at its maximum; thearmature, released from the poles and theaspringrelieyed cf- .pres*- sure. When the poles reverse ton move: forward, a high degreeof acceleration-must be. imparted to the armature, and unless the machineisop erated at a low speed, thehold of the-armature on the poles will. faill Fig. 8 illustrates how. I overcome this objectionable conditions A blade spring '59; operates to urge the armature forward, following it upuntil it is fully accelerated; This spring also serves to assure proper: and'like'contacts 1 for each forward throw: of'the armature;

The characteristics of the plate for reproducing a printing plate from a copy by my method is closely related to the means I employ in producing the depressions. t is quite essential that the texture of the plate contains minutepores evenly distributed, so that the substance displaced by the indenting tool in forming the depressions be absorbed in the increased density of the plate, instead of being displaced upward above the surface or sidewise into neighboring depressions.

Porous printing plates such as vulcanized fiber, treated micro-porous rubber, hard rubber containing a large percentage of wood flour and other preparations have been used. However, these possess undesirable properties, common to all or some of which are warping, absorption of moisture, excessive elasticity to indentation and fragility.

Porous malleable metal plates, especially of copper or bronze, produced in the well known art of powder metallurgy, having a porosity of the order of 20% to 30%, would otherwise be satisfactory for indenting with the tool, were it not for the open pores on the surface of these plates, which when inked and printed show white spots. The pores on the surface can, of course, be very much reduced and even eliminated in the process of production by employing higher pressures in compacting the metal powders, but then the resulting .plate density would not permit the absorption of the quantity of metal displaced for the high light effects. These require a porosity of the order of 20% to 30% as stated and roughly illustrated at 63 in Figs. 11 and 12 respectively.

To overcome the difficulty presented by the surface pores, I provide the surface with a thin continuous metallic layer 64, the same in kind as that of the plate or of other metals suitable for the purpose. This is done in one of several ways, such as by so-called tinning the surface; by placing a thin sheet of metal in thickness of the order of .001 of an inch against the bottom surface Of the mold employed for the production of these porous plates, against which the metal powders are then compressed by the high pressures used in this art; by continual grinding or sandpapering until the adjoining metal has been drawn or peened over the open pores and then polishing or by electrolytic deposition into the open pores after the surface of the plate in general has been rendered electrically non-conductive.

The porosity of the plates produced by powder metallurgy is controllable to a high degree and can be standardized as to percentage of porosity. This enables the production and supply of special plates for reproducing satisfactory prints from defective copies, namely such as are too fiat or such as are too contrasty.

It will be readily understood that the tool will penetrate deeper in a plate of greater porosity, diagrammatically illustrated in Fig. 12, than in one of less porosity, Fig. 11. The former would be advantageously used to reproduce flat copies and the latter contrasty copies. This is analogous to the soft and contrast photographic printing papers.

It is to be understood, of course, that references to pores in the plates, in the specification and claims, do not include blow-holes occurring in manufactured castings.

What I claim is:

l. A device for indenting surfaces to various depths in accordance with electrical impulses comprising an indenting tool, an indenting tool mount, means for reciprocating said tool mount substantially perpendicular to a work surface with substantial uniform reciprocations, means mounting said indenting tool on said mount for free bodily movement with respect thereto, magnetic means for causing said indenting tool to move with said mount in accordance with the amount of current supplied to said magnetic means, and spring means secured to said tool and extending beyond the working end of said indenting tool to prevent work engagement of said too-l when said magnetic means is inactive.

2. A device for indenting surfaces to various depths in accordance with electrical impulses comprising an indenting tool supported for free bodily movement to and from the work surface, a reciprocating drive, magnetic means for causing said too-l to move with said drive for penetrating said surface in accordance with the amount of current supplied to said magnetic means. spring means for urging said tool forward toward said surface when said tool is accelerating, and spring means secured to said tool and extending beyond the working end of said tool to prevent work engagement of said tool when said magnetic means is not activated by said control current. a

3. A device for forming depressions in the surface of a blank to various depths in accordance with electrical impulses comprising a fixed immovable electro-magnet, a movably free portion of the pole of said electro-magnet, means for reciprocating said free portion in close proximity to said electro-magnet in a direction perpendicular to the lines of magnetic flux passing into said free portion, an armature movably mounted with respect to said free portion, a tool connected to said armature for forming depressions in the surface of a blank, and a circuit for advancing said magnetic means for causing said armature and therefore said tool to be coupled with and to move with said free portion to penetrate said surface in accordance with the amount of current supplied to said electro-magnet.

OTTO W. GREENBERG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 199,568 Peters Jan. 22, 1878 518,826 Sachers Apr. 24, 1894 855,821 Summers June 4, 1907 874,183 Gordon et al Dec. 14, 1907 1,129,493 Jarniga-n Feb. 23, 1915 2,086,798 Greenberg July 13, 1937 2,092,765 Losier Sept. 14, 1937 2,332,737 Marvin Oct. 26, 1943 2,367,945 Jorgensen Jan. 23, 1945 

